From: Dennis Gnad <dennis.gnad@kit.edu>
To: Vince Weaver <vincent.weaver@maine.edu>
Cc: David Ahern <dsahern@gmail.com>, linux-perf-users@vger.kernel.org
Subject: Re: Understanding timestamps in perf.data
Date: Thu, 3 Sep 2015 16:46:54 +0200 [thread overview]
Message-ID: <55E85D5E.90400@kit.edu> (raw)
In-Reply-To: <alpine.DEB.2.20.1509030849190.3450@vincent-weaver-1.umelst.maine.edu>
On 03.09.2015 14:52, Vince Weaver wrote
>
> The kernel itself has trouble going to 100Hz without causing a lot of
> overhead and at 1kHz the NMI overhead gets high enough that the kernel
> throttles things down. I haven't investigated why that is, it might be a
> problem with how my tool is coded. For now I just gave up and am making
> masurements at 10Hz.
OK thanks for this information. I can probably now exclude the current
perf-interface of the kernel.
Maybe this is also interesting for you then:
In the meantime I got some information for the x86 architecture. There,
the performance counters can be read directly in userspace by the
interface over MSR's similar to readmsr/msrtool, where a reliable
interval of <10ms can be achieved. [1]
For ARM, there seems to exist some specialized driver "gator" which I
didn't take a closer look.
Anyhow, I am currently looking at a Power7 system, and don't know of any
other interfaces there than perf/oprofile. I will continue to try to
find some more information about that.
Best regards,
Dennis
[1] *F. Oboril*, J. Ewert, and M. B. Tahoori, "High-Resolution Online
Power Monitoring for Modern Microprocessors," in Proceedings of Design,
Automation & Test in Europe (*DATE*), 2015, France. Online available:
*http://cdnc.itec.kit.edu/downloads/Papers/Oboril15DATE.pdf
*
next prev parent reply other threads:[~2015-09-03 14:47 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-02 9:28 Understanding timestamps in perf.data Dennis Gnad
2015-09-02 13:43 ` David Ahern
2015-09-02 15:18 ` Dennis Gnad
2015-09-02 16:44 ` David Ahern
2015-09-02 17:00 ` Vince Weaver
2015-09-02 17:00 ` David Ahern
2015-09-03 7:19 ` Dennis Gnad
2015-09-03 12:52 ` Vince Weaver
2015-09-03 14:46 ` Dennis Gnad [this message]
2015-09-03 15:17 ` Vince Weaver
2015-09-02 19:23 ` Andi Kleen
2015-09-02 19:25 ` David Ahern
2015-09-03 9:50 ` Dennis Gnad
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